This invention relates to an accessory communication device for telephone sets, and particularly to a necklacetype accessory communication device having a microphone unit and a pair of earphones detachably combined to make electrical connections with a telephone set for convenient communication operations.
Conventionally, accessory communication devices for telephone sets are usually grouped into two types--a handset type and a headset type The handset type is simple and can be arranged on a telephone set for easy pick-up and hang-on made by a user during communication. However, the problem suffered by this known handset-type communication device is that said handset does not allow a user the free use of both hands during communication operations. As a result of great effort, the telecommunication industry developed a hands-free telephone set in order to overcome the above-mentioned problem. However, said hands-free telephone set suffers two major drawbacks. The first of these drawbacks being that no privacy can be maintained by the user during his/her conversation due to the intercom-like nature of such a telephone set. The second drawback being that because of the afore-mentioned intercom-like nature of the hands-free telephone set, use thereof is not only disturbing to others but is also easily affected by background noise.
In order to overcome the above-mentioned problems, a headset accessory communication device, as shown in FIG. 1, was produced. However, the headband lA cannot be suitably placed on the heads of various users and often causes some inconvenience, particularly to a lady's hairdo. In addition, no proper adjustment can be made on the receiver lB and the microphone unit IC, greatly affecting the quality of communication operations. (The German made BILSON VIKING 2318 and KHALDI 328 belong to this type of headset.)
In reaction to the problems which exist in the abovementioned headset, a kind of a single ear-mask-type headset, entitled STARTSET II, as shown in FIG. 2, was developed by the U. S. Plantronics Company. Although this ear-mask-type of headset has no headband, the overall weight of the ear mask E, the earpiece F and the microphone boom G all placed on a single ear of the user, is uncomfortable to bear and presents a great inconvenience to the user. Moreover, if a user wears a pair of glasses, the burden which the ear of the user must bear is increased.
For making further improvement on the above-mentioned prior art, a stethoscope-type accessory communication device, as shown in FIG. 3, was developed to satisfy the demand for conducting a headband-free and quiet communication operation. However, owing to the hanging-down force of the binaural-band 3A, the earpieces 3B of this stethoscope-type communication device must be firmly placed in the user ears, otherwise the earpieces 3B can easily slip out of the user's ears, causing considerable discomfort. In addition, the microphone unit 3C cannot make a telescopic movement and frequently requires to be adjusted so as to align with the user's mouth. (The same drawback is true for the STETOMIKE headset produced by U. S. DANAVOX Co., and therefore the product was not widely accepted in the market.)
As can be seen in the drawings of FIGS. 1 through 3, a common drawback shared by the above-mentioned prior art is that the conspicuous exposure of the receiving and transmitting components of the prior art can hardly allow a user to enjoy certain secrecy during communication operations.